1. Field of the Invention
This invention relates to a buckling-restrained brace, and more particularly to a dual-core self-centering buckling-restrained brace capable of increasing the amount in a change of the length of the apparatus and preventing buckling of a core unit.
2. Description of the Related Art
US 2012/0000147 discloses a dual-core self-centering energy dissipation brace apparatus, which includes a first core member configured as a rectangular steel tube, a second core member configured as a rectangular steel tube and disposed within the first core member, two inner abutment plates disposed respectively at two ends of the second core member, an outer sleeve disposed around the first core member and configured as a rectangular steel tube, two outer abutment plates disposed respectively at two ends of the outer sleeve, and two tensioning units. One of the tensioning units connects one of the inner abutment plates corresponding to one end of the outer sleeve to one of the outer abutment plates corresponding to the other end of the outer sleeve. The other of the tensioning units connects the other of the inner abutment plates to the other of the outer abutment plates. The first core member is provided with a plurality of energy dissipating plates. The outer sleeve is provided with angle steels connected to the energy dissipating plates by lock bolts for energy dissipating purposes.
When an external force is applied to the apparatus, it is transmitted from a building onto the first core member or one of the outer abutment plates, and is transmitted out along a path including one of the tensioning units, one of the inner abutment plates, the second core member, the other of the inner abutment plates, the other of the tensioning units, the other of the outer abutment plates, and the outer sleeve. During the transmission of the external force, relative movement occurs among the first and second core members and the outer sleeve, such that energy is dissipated through the energy dissipating plates, the angle steels, and the lock bolts. In addition, each of the tensioning units has an elongation amount δ, so that the first core member and the outer sleeve move relative to each other by a distance 2δ. Hence, the maximum allowable elongation amount of the apparatus when subjected to an earthquake is increased. In this manner, energy can be dissipated through friction.
Upon occurrence of an earthquake, the residue stress of the building can be eliminated by return force of the tensioning units. However, when the apparatus is subjected to a plurality of earthquakes, such energy dissipating members (including the energy dissipating plates, the angle steels, and the lock bolts) experience serious wear, which reduces their energy dissipating efficiency and results in a need for frequent replacement, maintenance, and repair.